CVE-2017-2253 in Yahoo! Toolbar
Summary
by MITRE
Untrusted search path vulnerability in Installer of Yahoo! Toolbar (for Internet explorer) v8.0.0.6 and earlier, with its timestamp prior to June 13, 2017, 18:18:55 allows an attacker to gain privileges via a Trojan horse DLL in an unspecified directory.
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Analysis
by VulDB Data Team • 10/26/2019
The vulnerability identified as CVE-2017-2253 represents a critical untrusted search path issue within the Yahoo! Toolbar installer component for Internet Explorer versions 8.0.0.6 and earlier. This flaw stems from the installer's improper handling of dynamic link library (dll) loading mechanisms, where the installation process fails to validate or sanitize the search path used to locate required system components. The vulnerability specifically affects installations with timestamps prior to June 13, 2017, 18:18:55, indicating a time-based window of exposure that aligns with the software's release cycle and patching timeline. The installer's behavior creates an environment where malicious actors can exploit the trust relationship between the installation process and system directories, allowing for privilege escalation through the strategic placement of malicious dll files in unspecified directories.
The technical exploitation of this vulnerability operates through a Trojan horse attack vector where an attacker places a specially crafted malicious dll file in a directory that the installer's search path will traverse before reaching legitimate system directories. This occurs because the installer does not properly implement secure search path resolution, instead relying on the default system PATH behavior which may include user-writable directories. The vulnerability manifests when the installer attempts to load necessary dll components, inadvertently executing the malicious code with the privileges of the user performing the installation. This represents a classic dll hijacking scenario that aligns with CWE-426, which specifically addresses the insecure handling of dynamic link library loading operations. The flaw essentially allows for privilege escalation from standard user privileges to potentially elevated system privileges, depending on the installation context and user permissions.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass broader security implications for enterprise environments and individual users alike. In enterprise settings, the vulnerability could enable attackers to establish persistent access through the installation of malicious toolbars that persist across system reboots and user sessions. The vulnerability's timing window creates a specific attack surface where legacy installations remain exposed, particularly in organizations that delay patching or maintain older software versions for compatibility reasons. The attack requires minimal sophistication from an attacker's perspective, as it only requires placing a malicious dll file in an appropriate directory rather than requiring complex exploitation techniques. This characteristic makes the vulnerability particularly dangerous as it can be exploited by adversaries with limited technical expertise. The vulnerability also demonstrates the broader risk associated with legacy software components that continue to receive installation support but lack proper security hardening measures.
Mitigation strategies for CVE-2017-2253 must address both immediate remediation and long-term security posture improvements. The primary recommendation involves immediate patching or uninstallation of affected Yahoo! Toolbar versions, as the vulnerability cannot be effectively mitigated through configuration changes alone. Organizations should implement strict software inventory controls to identify and remove legacy applications that may contain similar vulnerabilities. The remediation process should include comprehensive system scanning to detect any malicious dll files that may have already been installed as part of an attack. Security controls should be enhanced to monitor and restrict dll loading operations, particularly in user-writable directories, implementing application whitelisting solutions that prevent unauthorized dll execution. Additionally, system administrators should consider implementing secure coding practices for installation components, ensuring that all search paths are properly validated and that the installer uses absolute paths for critical components rather than relying on default system behavior. This vulnerability highlights the importance of following security best practices outlined in the ATT&CK framework, particularly in the area of privilege escalation and persistence mechanisms, where the exploitation of installer vulnerabilities represents a common attack vector that security teams must proactively defend against through comprehensive patch management and software lifecycle controls.